1. Field of the Invention
The present general inventive concept relates to a stereoscopic image signal, and more particularly, to a method of generating a progressive stereoscopic image signal and a method of scaling the same.
2. Description of the Related Art
In general, a stereoscopic image is based on a stereo view angle by human eyes. Binocular parallax, which is due to the right and left eyes being about 65 mm apart from each other, is the most critical factor of a feeling of solidity.
There are two types of stereoscopic displays, one with glasses and another without glasses. The non-glasses type stereoscopic display obtains a stereoscopic image by separating a left-eye image from a right-eye image without glasses.
The glasses type stereoscopic display displays left and right parallax images on a direct-view display or projector with directions of polarization changed or in a time-divisional manner. The stereoscopic image can be seen with polarization glasses or liquid-crystal shutter glasses.
The non-glasses type stereoscopic display includes a parallax barrier type, a lenticular type, a polarization multiplexing type, etc.
The parallax barrier type stereoscopic display displays images for individual eyes alternatively in the horizontal direction by the space of a pixel, and then the displayed images are seen through a vertical grating, or a so called “barrier,” Thus the displayed images are separated from each other by the barrier to be seen by the left and right eyes respectiveiy so that a stereoscopic image is seen.
In the polarization multiplexing type stereoscopic display, a progressive stereoscopic image signal, in which the left-eye image signal and the right-eye image signal are alternately arranged in scanning lines, is displayed and then polarized by passing the progressive stereoscopic image signal through two polarization filters with different polarizing characteristics so that the left eye can only see odd-numbered scanning lines of the progressive stereoscopic image signal and the right eye can only see even-numbered scanning lines of the progressive stereoscopic image signal. Examples of a stereoscopic display device using the polarization multiplexing method are disclosed in Korean Patent Laid-open Publication Nos. 1999-80351 (published on Jan. 5, 1999) and 2002-96203 (published on Dec. 31, 2002) and in Japanese Patent Laid-open Publication No. 09-149434 (published on Jun. 6, 1997 etc.
FIG. 1 is a diagram illustrating a conventional polarization multiplexing type stereoscopic display device. Referring to FIG. 1, the conventional stereoscopic display device includes a display panel 102 which displays a progressive stereoscopic image signal and a polarization film unit 104 which is comprised of a plurality of first polarization lines 112 and a plurality of second polarization lines 114. The first and second polarization lines 112 and 114 are alternately arranged in the polarization film unit 104 in a vertical scanning direction and have different polarization characteristics. Specifically, the first polarization lines 112 have first polarization characteristics, and the second polarization lines 114 have second polarization characteristics. The first polarization lines 112 are used for providing a user with a left-eye image, and the second polarization lines 114 are used for providing the user with a right-eye image.
The conventional stereoscopic display device displays a progressive stereoscopic image signal and polarizes the displayed image signal through the first and second polarization lines 112 and 114 so that a user views odd-numbered scanning lines of the stereoscopic image signal with his or her left eye and views even-numbered scanning lines of the stereoscopic image signal with his or her right eye.
FIG. 2 is a diagram illustrating a progressive stereoscopic image signal displayed by the conventional stereoscopic display device of FIG. 1. Referring to FIG. 2, the progressive stereoscopic image signal has a size N1×N2. Odd-numbered scanning lines of the progressive stereoscopic image signal belong to a left-eye image signal, and even-numbered scanning lines of the progressive stereoscopic image signal belong to a right-eye image signal. Here, the left-eye image signal and the right-eye image signal are taken by a left-eye image camera and a right-eye image camera, respectively, which are separated from each other by the same distance as the distance between human eyes
FIG. 3 is a block diagram illustrating a conventional apparatus for generating the progressive stereoscopic image signal of FIG. 2. Referring to FIG. 3, the conventional apparatus for generating the progressive stereoscopic image signal includes a first scaler 302, which receives the left-eye-image signal and scales the received left-eye image signal up or down, a second scaler 304, which receives the right-eye image signal and scales the received right-eye image signal up or down, and a multiplexer 316, which generates the progressive stereoscopic image signal by multiplexing the up-scaled or down-scaled left-eye image signal and the up-scaled or down-scaled right-eye image signal.
For a three-dimensional (3D) stereo broadcast, an interlaced stereoscopic image signal whose odd-numbered fields belong to the left-eye image signal and whose even-numbered fields belong to the right-eye image signal is transmitted. Standard digital TV sets provide a fixed resolution of 720×408 i/p or 1920×1080 i/p where i stands for ‘interlaced,’ and p stands for ‘progressive.’
In general, display devices adopt a progressive scanning method and can render an image with various resolutions. Thus, in order to make a display device compatible with a 3D stereo broadcast, a de-interlacing operation and a scaling operation are needed to convert the interlaced stereoscopic image signal into the progressive stereoscopic image signal.
Referring to FIG. 3, the first and second scalers 302 and 304 perform a scaling operation. Specifically, each of the first and second scalers 302 and 304 may scale up an input image signal in a vertical scanning direction according to a resolution provided by a display device, by using either a bilinear interpolation method or a convolution interpolation method with reference to the degree of correlation between adjacent scanning lines of the image signal.
The multiplexer 316 performs interlacing.
FIG. 4 is a diagram illustrating the operation of the multiplexer 316 of FIG. 3. Referring to FIG. 4, the multiplexer 316 obtains the progressive stereoscopic image signal of FIG. 2 by multiplexing a left-eye image signal 402 and a right-eye image signal 404 so that the scanning lines of the left-eye image signal 402 and the scanning lines of the right-eye image signal 404 are alternately arranged.
As described above, the conventional apparatus of FIG. 3 for generating a progressive stereoscopic image signal includes the first and second scalers 302 and 304, which scale up or down the left-eye image signal 402 and the right-eye image signal 404, respectively. Each of the first and second scalers 302 and 304 includes a memory, in which an image signal is stored, and an interpolator, which reads each of a plurality of scanning lines of the image signal from the memory and generates new scanning lines through interpolation.
The conventional apparatus for generating a progressive stereoscopic image signal, however, has a relatively complex display device structure and is costly because it includes the two scalers 302 and 304.